Metal and polymer substrates having a powder basecoat and liquid topcoat

ABSTRACT

Composite coated metal and/or polymer substrates are provided having a powder basecoat thereon formed from at least one film-forming material comprising a thermosettable polyester and a curing agent; at least one reaction product of at least one cyclic carboxylic acid anhydride, at least one alkene and at least one reactant selected from the group consisting of primary amines, aliphatic polyamines, primary amino alcohols, alcohols, isocyanates and mixtures thereof, the copolymer having a number average molecular weight ranging from about 1,000 to about 20,000; and at least one flow control agent; and a topcoat deposited from a liquid or powder slurry topcoating composition applied over the basecoat to form a composite coating providing good adhesion and chip and cratering resistance.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to metal and polymer substrates coated with apowder basecoat that is compatible with a wide variety of liquidtopcoats, providing good intercoat adhesion and resistance to chippingand cratering.

Today's automobile bodies are treated with multiple layers of coatingsthat not only enhance the appearance of the automobile, but also provideprotection from corrosion, chipping, ultraviolet light, acid rain andother environmental conditions that can deteriorate the coatingappearance and underlying car body.

The formulations of these coatings can vary widely. However, a majorchallenge that faces all automotive manufacturers is how to rapidlyapply and cure these coatings with minimal capital investment and floorspace, which is valued at a premium in manufacturing plants. Use ofpowder coatings is desirable because they emit very low amounts ofvolatile materials to the environment when cured and excess material canbe easily recycled.

For example, U.S. Pat. No. 6,715,196 discloses a method of coatingmetallic substrates with a weldable primer coating having greater than10 volume percent of electroconductive pigment, powder basecoat andclear top coat.

Despite recent improvements in color-plus-clearcoating systems, thereremains a need in the automotive coatings art for composite coatings fordirect-to-metal or polymer applications having good intercoat adhesionas well as good cratering and chipping resistance. Moreover, it would beadvantageous to provide a coating system in which the powder basecoat iscompatible with a wide variety of conventional liquid and powder slurrytopcoats to lower VOC of the overall painting process yet minimizeretrofit expenses for existing automotive coating assembly lines.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a composite coatedsubstrate comprising:

(a) a substrate selected from the group consisting of metallicsubstrates, polymeric substrates and mixtures thereof;

(b) a basecoat deposited upon a surface of the substrate, the basecoatbeing formed from a powder basecoating composition comprising:

-   -   (i) at least one film-forming material comprising a        thermosettable polyester and a curing agent;    -   (ii) at least one reaction product of at least one cyclic        carboxylic acid anhydride, at least one alkene and at least one        reactant selected from the group consisting of primary amines,        aliphatic polyamines, primary amino: alcohols, alcohols,        isocyanates and mixtures thereof, the copolymer having a number        average molecular weight ranging from about 1,000 to about        20,000; and    -   (iii) at least one flow control agent; and

(c) a topcoat deposited from a liquid or powder slurry topcoatingcomposition applied over the basecoat to provide a composite coatedsubstrate.

Another aspect of the present invention is a process for coating ametallic or polymeric substrate, comprising the steps of:

(a) applying a powder basecoating composition to a surface of a metallicor polymeric substrate,

the first powder basecoating composition comprising:

-   -   (i) at least one film-forming material comprising a        thermosettable polyester and a curing agent;    -   (ii) at least one reaction product of at least one cyclic        carboxylic acid anhydride, at least one alkene and at least one        reactant selected from the group consisting of primary amines,        aliphatic polyamines, primary amino alcohols, alcohols, is        cyanates and mixtures thereof, the copolymer having a number        average molecular weight ranging from about 1,000 to about        20,000; and    -   (iii) at least one polymer flow control agent, to form a powder        basecoat on the surface of the substrate;

(b) at least partially curing the powder basecoat to form a basecoat;

(c) applying a liquid or powder slurry topcoating composition over atleast a portion of the basecoat; and

(d) at least substantially curing the topcoating composition and anyuncured basecoat to provide a composite coating upon the surface of thesubstrate.

Other than in the operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

DETAILED DESCRIPTION

The present invention relates to composite coated substrates useful aspanels and parts, particularly for automotive applications, havingstriking visual effects, good gloss, durability, scratch and humidityresistance and is resistant to overspray incompatibility coatingdefects, such as cratering, chipping and lack of intercoat adhesion. Thecomposite coating can be applied directly to metal and/or polymersubstrates, eliminating the need for primer coatings. Alternatively, thecomposite coating can be applied over an electrodeposited primer coatingor primer coating having less than 10 volume percent of weldableelectroconductive pigment. The composite coating comprises a powderbasecoating that is compatible with a wide variety of conventionalliquid or powder slurry topcoats. Another advantage of the invention isthe ability to produce these panels and parts using a virtually zero VOCbasecoat system with high utilization rates.

The composite coated substrates of the present invention have acomposite coating applied over at least a portion of a substrate.Suitable substrates are selected from the group consisting of metallicsubstrates, polymeric substrates, such as thermoset materials andthermoplastic materials, and combinations thereof.

Useful metal substrates include ferrous metals, non-ferrous metals, andcombinations thereof. Suitable ferrous metals include iron, steel andalloys thereof. Non-limiting examples of useful steel materials includecold rolled steel, zinc coated steels such as hot dip galvanized andelectrogalvanized steel, stainless steel, pickled steel, zinc-iron alloysuch as GALVANEAL, zinc-aluminum alloys coated over steel such asGALVALUME, and GALFAN, and combinations thereof. It is possible fordifferent portions of the same substrates to be different forms offerrous metal, for example, for the zinc coating to be applied to onlycertain portions or one side of the steel substrate. Useful non-ferrousmetals include aluminum, zinc, magnesium, and alloys thereof.Combinations or composites of ferrous and non-ferrous metals can also beused. Preferred metallic substrates are anti-corrosive steels such asthe zinc coated steels and the zinc-iron alloy and the zinc-aluminumalloys mentioned above.

Useful thermoset materials include polyesters, epoxides, phenolics,polyurethanes such as reaction injected molding urethane (RIM) thermosetmaterials and mixtures thereof. Useful thermoplastic materials includethermoplastic polyolefins such as polyethylene and polypropylene,polyamides such as nylon, thermoplastic polyurethanes, thermoplasticpolyesters, acrylic polymers, vinyl polymers, polycarbonates,acrylonitrile-butadiene-styrene (ABS) copolymers, ethylene propylenediene monomer (EPDM) rubber, copolymers and mixtures thereof.

Preferably, the substrates are used as components to fabricateautomotive vehicles, including but not limited to automobiles, trucksand tractors. The substrates can have any shape, but are preferably inthe form of automotive body components such as bodies (frames), hoods,doors, fenders, bumpers and/or trim for automotive vehicles.

The present invention first will be discussed generally in the contextof coating a metallic automobile body. One skilled in the art wouldunderstand that the process of the present invention also is useful forcoating non-automotive metal and/or polymeric components, which will bediscussed below.

Before depositing the coatings upon the surface of the metal substrate,it is preferred to remove dirt, oil, or foreign matter from the metalsurface by thoroughly cleaning and degreasing the surface. The surfaceof the metal substrate can be cleaned by physical or chemical means,such as mechanically abrading the surface or cleaning/degreasing withcommercially available alkaline or acidic cleaning agents which are wellknown to those skilled in the art, such as sodium metasilicate andsodium hydroxide. Non-limiting examples of suitable alkaline cleaningagents include CHEMKLEEN 163 and CHEMKLEEN 177 phosphate cleaners thatare commercially available from PPG Industries, Inc. of Pittsburgh, Pa.

Following the cleaning step, the metal substrate is usually rinsed withwater, preferably deionized water, in order to remove any residue. Themetal substrate can optionally be dried using an air knife, by flashingthe water off by brief exposure to a high temperature, or by passing themetal between squeegee rolls.

Following the cleaning and optional drying steps, the metal substratemay be optionally pretreated with a thin layer of pretreatment. Theadvantages of pretreatment include protection of the metallic substratefrom corrosion and improvement of adhesion of subsequent coating layersto the substrate. Pretreatments may be chrome containing or preferablychrome-free. The choice of pretreatment is generally determined by thesubstrate and environmental considerations. Appropriate pretreatmentsare well known to those skilled in the art. An example of a suitablechrome pretreatment is Granodine 1415A available from Henkel SurfaceTechnologies, NA. An example of a chrome-free pretreatment is Nupal456BZ available from PPG Industries, Inc. or CHEMFOS 700 zinc phosphatepretreatment.

The pretreatment solution is applied to the surface of the metalsubstrate by any conventional application technique, such as spraying,immersion or roll coating in a batch or continuous process. Thetemperature of the treating solution at application is typically about10° C. to about 85° C., and preferably about 15° C. to about 40° C. ThepH of the preferred treating solution at application generally rangesfrom about 2.0 to about 9.0, and is preferably about 3 to about 5.

The film coverage of the residue of the pretreatment coating generallyranges from about 0.1 to about 1000 milligrams per square meter (mg/m²),and is preferably about 1 to about 400 mg/m².

Hereafter, the term “substrate” shall refer to the cleaned, optionallypretreated, substrate.

Preferably, the surface of the substrate is essentially free ofconductive weldable primer coating prior to application of the compositecoating, i.e., the surface of the substrate has less than about 5percent of its surface area coated with conductive weldable primer andmore preferably less than about 2 percent. More preferably, the surfaceof the substrate is free of conductive weldable primer coating prior toapplication of the composite coating.

As used herein, “conductive weldable primer” or “conductive weldableprimer coating” means a conductive, weldable coating, such as isdescribed in U.S. Pat. No. 6,715,196 (incorporated by reference herein),that is formed from a composition comprising one or moreelectroconductive pigments which provide electroconductivity to theweldable coating and one or more binders which adhere theelectroconductive pigment to the substrate. Such electroconductivepigments include zinc, iron phosphide, aluminum, iron, graphite, nickel,tungsten and mixtures thereof, such as Stolberger ZINCOLI as ZINCOLI S620 zinc particles, US Zinc Superfine 7 zinc dust or Ferrophos Microfinegrade 2132 iron phosphide from Glenn Springs Holdings of Lexington, Ky.Such a composition comprises a substantial amount of electroconductivepigment, generally greater than about 10 volume percent and usuallyabout 30 to about 60 volume percent on a basis of total volume ofelectroconductive pigment and binder.

In another embodiment, the substrate can be coated with a powder primer,such as are disclosed in U.S. Pat. Nos. 4,804,581; 5,212,245 and5,248,400 (incorporated by reference herein). Another example of auseful powder primer is ENVIROCRON PCV70118 powder primer available fromPPG Industries, Inc.

In another embodiment, the surface of the substrate can be coated withan electrodeposited primer coating prior to application of the compositecoating. Suitable electrodepositable coating compositions includeconventional anionic or cationic electrodepositable coatingcompositions, such as epoxy or polyurethane-based coatings discussed inU.S. Pat. Nos. 6,217,674, 5,530,043; 5,760,107; 5,820,987 and 4,933,056,incorporated herein by reference. One skilled in the art wouldunderstand that such an electrodepositable coating composition isessentially free of electroconductive pigments, i.e., less than about 5weight percent, preferably less than about 2 weight percent and morepreferably is free of electroconductive pigments, on a basis of totalweight of the electrodepositable coating composition, as suchelectroconductive materials would interfere with the electrodepositionprocess. Methods of application and suitable coating thicknesses arewell known to those skilled in the art and are disclosed in theforegoing references.

To provide added cost savings, in another embodiment the surface of thesubstrate is essentially free of electrodeposited primer coating priorto application of the composite coating, i.e., the surface of thesubstrate has less than about 5 percent of its surface area coated withelectrodeposited primer and more preferably less than about 2 percent.In another embodiment, the surface of the substrate is free ofelectrodeposited primer coating prior to application of the compositecoating.

An advantage of the composite coating of the present invention is thatit can be applied directly to bare metal, eliminating the need forprimer coating. Besides the obvious cost savings of eliminating acoating layer and saving energy by eliminating a drying step,elimination of electrodeposition of primer coating can significantlyreduce plant infrastructure expense. Preferably, the bare metal iscold-rolled steel or galvanized steel.

In the present invention, a basecoat is deposited upon a surface of thesubstrate. The basecoat is formed from a powder basecoating compositioncomprising at least one film-forming material.

Preferably, the polymeric, film-forming material of the powderbasecoating composition is of the thermoset type and comprises: (a) oneor more polymers having reactive functional groups and; (b) one or morecuring agents selected to react with the functional groups of (a).

At least one of the polymers (a) having reactive functional groups is athermosettable polyester. The thermosettable polyester can have reactivefunctional groups selected from the group consisting of hydroxyl,carboxylic acid, epoxy, carbamate, amide, carboxylate and combinationsthereof.

Preferably, the thermosettable polyester has carboxylic acidfunctionality. Monomers for the synthesis of polyester polymers havingcarboxylic acid functionality suitable for use in the powder coatingcompositions of the present invention are chosen such that the resultingpolyester polymer has a T_(g) greater than 40° C.

Among the carboxylic acid group-containing polyesters which may be usedare those based on a condensation reaction of aliphatic polyols,including cycloaliphatic polyols, with aliphatic and or aromaticpolycarboxylic acids and anhydrides. Examples of suitable aliphaticpolyols include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol,1,6-hexanediol, neopentyl glycol, cyclohexane dimethanol,trimethylolpropane, and the like. Suitable polycarboxylic acids andanhydrides include succinic acid, adipic acid, azelaic acid, sebacicacid, terephthalic acid, isophthalic acid, tetrahydrophthalic acid,hexahydrophthalic acid, trimellitic acid, and anhydrides of such acids.

The polyol and the acid or anhydride are reacted together with an excessof acid over alcohol so as to form a polyester which has free carboxylicgroups. Preferably, the carboxylic acid group-containing polyester willhave an acid number of from about 20 to about 80, more preferably fromabout 30 to about 75, and will be an amorphous solid at roomtemperature. The polyester is further characterized as having a T_(g) offrom about 30° C. to about 85° C., preferably from about 40° C. to about75° C.

The T_(g) of a polymer is a measure of the hardness and melt flow of thepolymer. The higher the T_(g), the less the melt flow and the harder thecoating. T_(g) is described in Principles of Polymer Chemistry (1953),Cornell University Press. The T_(g) can be actually measured or it canbe calculated as described by Fox in Bull. Amer. Physics Soc., 1, 3,page 123 (1956). T_(g), as used herein, refers to actually measuredvalues. For measurement of the T_(g) of a polymer, differential scanningcalorimetry (DSC) can be used (a rate of heating of 10° C. per minute,with T_(g) taken at the first influxation point).

If the T_(g) of the polyester is below 30° C., the polymer and a powdercoating composition including such a polymer can tend to be sticky anddifficult to handle. If the T_(g) is above 85° C., the melt flow of thepolyester is low and the coating may have poor appearance.

Examples of suitable carboxylic acid group-containing polyester polymersare those described in U.S. Pat. No. 4,801,680 at col. 5, line 65 tocol. 7, line 39, hereby incorporated by reference. A preferredcarboxylic acid functional polyester is DSM P880, which is availablefrom DSM.

In addition to the thermosettable polyester, the powder basecoatingcomposition can further comprise other oligomers or polymers containingfunctional groups such as hydroxyl, carboxylic acid, epoxy, carbamate,amide and carboxylate functional groups.

The use in powder coatings of acrylic, polyester, polyether andpolyurethane oligomers and polymers having hydroxyl functionality iswell known in the art. Monomers for the synthesis of such oligomers andpolymers are chosen such that the resulting oligomers and polymers havea T_(g) greater than 40° C. Examples of such oligomers and polymershaving hydroxyl functional groups suitable for use in the powder coatingcompositions of the present invention are those described in U.S. Pat.No. 5,646,228 at column 5, line 1 to column 8, line 7, incorporated byreference herein.

The use in powder coatings of acrylic polymer shaving carboxylic acidfunctionality is well known in the art. Monomers for the synthesis ofthe acrylic polymers having carboxylic acid functionality suitable foruse in the powder coating compositions of the present invention arechosen such that the resulting acrylic polymer has a T_(g) greater than40° C. Examples of carboxylic acid group containing acrylic polymers arethose described in U.S. Pat. No. 5,214,101 at col. 2, line 59 to col. 3,line 23, incorporated by reference herein.

Also useful in powder coating compositions are acrylic, polyester andpolyurethane polymers containing carbamate functional groups and epoxyfunctional groups, such as those well known in the art. Examples of suchpolymers having carbamate functionality suitable for use in the powdercoating compositions of the invention are described in internationalapplication WO 94/10213. Examples of polymers having epoxy functionalitysuitable for use in powder coating compositions are described in U.S.Pat. No. 5,407,707, incorporated by reference herein. Monomers for thesynthesis of such polymers for use in the powder coating compositionsare chosen such that the resulting polymer has a high T_(g), that is, aT_(g) greater than 40° C.

Suitable curing agents for the powder basecoating composition includeaminoplasts, blocked polyisocyanates, polyacids, polyepoxides, polyols,polyanhydrides, hydroxyalkylamides, and mixtures thereof.

Blocked isocyanates as curing agents for (OH) and primary and/orsecondary amino group containing materials are well known in the art.Examples of blocked isocyanates suitable for use as curing agents in thepowder coating compositions of the present invention are those describedin U.S. Pat. No. 4,988,793, col. 3, lines 1 to 36, incorporated byreference herein.

Polyepoxides as curing agents for (COOH) functional group containingmaterials are well known in the art. Examples of polyepoxides suitablefor use as curing agents in the powder coating compositions of thepresent invention are those described in U.S. Pat. No. 4,681,811 at col.5, lines 33 to 58, incorporated by reference herein.

Polyacids as curing agents for epoxy functional group containingmaterials are well known in the art. Examples of polyacids suitable foruse as curing agents in the powder coating compositions of the presentinvention are those described in U.S. Pat. No. 4,681,811 at col. 6, line45 to col. 9, line 54, incorporated by reference herein.

Polyols, that is, material having an average of two or more hydroxylgroups per molecule, can be used as curing agents for (NCO) functionalgroup containing materials and anhydrides, and are well known in theart. Polyols for use in the powder coating compositions of the presentinvention are selected such that the resultant material has a high glasstransition temperature, i.e., greater than 50° C.

Beta-hydroxyalkylamide materials as crosslinkers for carboxylicacid-functional polymers (a) are disclosed in U.S. Pat. No. 4,801,680,incorporated by reference herein. The hydroxyl functionality of thebeta-hydroxyalkylamide should be on an average basis at least two,preferably greater than two, and more preferably from greater than twoup to about four in order to obtain optimum curing response.

The beta-hydroxyalkylamide materials can be depicted structurally asfollows:

wherein R₁ is H or C₁-C₅ alkyl; R₂ is H, C₁-C₅ alkyl or:

wherein R₁ is as described above; A is a bond, monovalent or polyvalentorganic radical derived from a saturated, unsaturated or aromatichydrocarbon including substituted hydrocarbon radicals containing from 2to 20 carbon atoms, m is equal to 1 to 2, n is equal to 0 or 2, and m+nis at least 2, preferably greater than 2, usually within the range offrom 2 up to and including 4. Preferably, A is an alkylene radical—(CH₂)_(x)— where x is from 2 to 12, preferably from 4 to 10. Apreferred beta-hydroxyalkylamide is N,N,N′,N′-tetrakis(2-hydroxyethyl)adipamide commercially available from Ems-Chemie AG, Switzerland underthe trade name, PRIMID XL-552.

The beta-hydroxyalkylamide can be prepared by reacting a lower alkylester or mixture of esters of carboxylic acids with abeta-hydroxyalkylamine at a temperature ranging from ambient temperatureup to about 200° C., depending on the choice of reactants and thepresence or absence of a catalyst. Suitable catalysts include basecatalysts such as sodium methoxide, potassium methoxide, sodiumbutoxide, potassium butoxide sodium hydroxide, potassium hydroxide andthe like, present in amounts of about 0.1 to about 1 percent by weightbased on the weight of the alkyl ester.

To bring about the most effective cure of the powder coatingcomposition, the equivalent ratio of beta-hydroxyalkylamide (hydroxyequivalents) to carboxy-containing polyester (carboxylic acidequivalents) is preferably from about 0.6 to 1.6:1, more preferably from0.8 to 1.3:1. Ratios outside the range of 0.6 to 1.6:1 are undesirablebecause of poor cure.

Anhydrides as curing agents for epoxy functional group containingmaterials are well known in the art. Examples of such curing agentsinclude trimellitic anhydride, benzophenone tetracarboxylic dianhydride,pyromellitic dianhydride, tetrahydrophthalic anhydride, and the like asdescribed in U.S. Pat. No. 5,472,649 at col. 4, lines 49 to 52,incorporated by reference herein.

Aminoplasts as curing agents for OH, COOH and carbamate functional groupcontaining materials are well known in the art. Examples of such curingagents suitable for use in the present invention are aldehydecondensates of glycoluril, which give high melting crystalline productsuseful in powder coatings. While the aldehyde used is typicallyformaldehyde, other aldehydes such as acetaldehyde, crotonaldehyde, andbenzaldehyde can be used.

The powder basecoating composition comprises at least one reactionproduct of at least one cyclic carboxylic acid anhydride, at least onealkene and at least one reactant selected from the group consisting ofprimary amines, aliphatic polyamines, primary amino alcohols, alcohols,isocyanates and mixtures thereof. The copolymer has a number averagemolecular weight ranging from about 1,000 to about 20,000, preferablyabout 3,000 to about 10,000, and more preferably about 3,000 to about6,000, and most preferably about 2,000 to about 2,500.

Non-limiting examples of suitable cyclic carboxylic acid anhydridesinclude maleic anhydride (preferred), chloromaleic anhydride,dichloromaleic anhydride, bromomaleic anhydride, citraconic anhydride,dimethylmaleic anhydride, ethylmaleic anhydride, itaconic anhydride,vinylsuccinic anhydride and vinyl trimellitate anhydride.

Suitable alkenes include cycloalkenes, alpha olefins, vinyl monomers,esters of acrylic acid or methacrylic acid, and mixtures thereof.

Examples of suitable alpha olefins include 1-hexene, 1-heptene,1-octene, 1-nonene, 1-decene (preferred), 2-methyl-1-butene,2-ethyl-1-butene, 2-ethyl-1-pentene, 2-methyl-1-pentene and2-ethyl-1-hexene.

The reaction product can be considered an essentially alternatingcopolymer of the cyclic carboxylic acid anhydride and alkene.Theoretically, one mole of the cyclic carboxylic acid anhydride orsubstituted cyclic carboxylic acid anhydride is added to one mole of thealkene to obtain the copolymer. However, a molar excess of the alkeneover the cyclic carboxylic acid anhydride is preferably employed. Thereaction is carried out by heating the reactants together, preferably inthe presence of an organic solvent and in the presence of a free radicalinitiator, e.g., an organic peroxide such as tertiary amylperoxyacetate, tertiary butyl perbenzoate and the like, or an azocompound such as azobisisobutyronitrile and the like at a temperaturegenerally up to the reflux of the alkene, generally temperatures fromabout 30° C. to about 220° C., preferably from about 80° C. to 180° C.for a time sufficient to complete the copolymerization, generally, aperiod of time varying between 1 to 24 hours, preferably 1 to 3 hours.The organic peroxide free radical initiators are preferred.

The reaction product generally has a number average molecular weight offrom about 1,000 to about 20,000, preferably from about 3,000 to about10,000, and more preferably from 3,000 to 6,000. The number averagemolecular weight of the copolymers can be determined by gel permeationchromatography (GPC) using a polystyrene standard. By such method, it isnot the actual molecular weight that is measured but an indication ofthe molecular weight as compared to polystyrene. The values that areobtained are commonly referred to as polystyrene numbers, however, forthe purposes of this application, they are referred to as molecularweights. Molecular weights (number average) less than 1,000 areundesirable as the copolymer loses surface activity, i.e., loss of flowcontrol properties, whereas molecular weights greater than about 10,000are less desirable and greater than about 20,000 are undesirable becauseof detrimental flow properties due to high viscosity.

The reaction product is chemically modified by from about 0.5 to about100 mole percent of a reactant selected from the group consisting ofprimary amines, aliphatic polyamines, primary amino alcohols, alcohols,isocyanates and mixtures thereof, based on moles of the anhydridefunctional groups in the copolymer. Preferably, the reaction product ischemically modified by from about 2 to about 10 mole percent of thereactant discussed above.

Chemical modification with an alcohol forms the partial ester or halfester derivatives, while chemical modification with a primary amineforms the imide. Among the alcohols that can be used are alkanols,preferably alkanols containing from 1 to about 10 carbon atoms such asmethanol, ethanol, propanols, butanols, pentanols, hexanols, heptanols,octanols and the like. More preferably, the alkanol is methanol,ethanol, butanol, or 2-ethylhexanol. Aryl alkanols, such as benzylalcohol, phenethyl alcohol and phenyl propyl alcohol, alkylglycols, suchas, ethylene glycol or propylene glycol, and substituted alkyl glycols,such as, the monoethylether of ethylene glycol, monobutylether ofethylene glycol, and monohexylether of ethylene glycol can also besuitable alcohols to form the half esters of the anhydride groups. Thealcohols may also be a tertiary amine having at least one alkanolradical such as 2-dimethylaminoethanol, 1-diemthylaminomethylpropanol,2-diethylaminoethanol and the like, or a diglycol amine, such asdimethyl or diethyl (amino ethoxy)ethanol. Chemical modification, i.e.,esterification, by an alcohol can be accomplished by heating thecopolymer and the alcohol together at a temperature of 100° C. to 150°C., optionally using a catalyst, such as sodium methoxide, to expeditethe anhydride ring opening.

The copolymer can also be chemically modified with primary amines, suchas butylamine, isobutylamine, propylamine, isopropylamine, ethylamine,methylamine and pentylamine, aliphatic polyamines, such asN,N-dimethylaminopropylamine, N,N-dimethylaminoethylamine,N,N-diethylaminopropylamine, N,N-diethylaminoethylamine and the like, orprimary aminoalcohols such as ethanolamine (preferred) and propanolamineand the like. Primary amines, such as aliphatic polyamines, e.g.,N,N-dimethylaminopropylamine, yield an imide-modified anhydride withpendent tertiary amino groups, which may act as a catalyst for epoxyreactions, and increase the crosslink density and resistance propertiesof the cured coating. Primary aminoalcohols can yield an imide-modifiedanhydride with pendent alcohol functionality.

Examples of suitable isocyanates include alkyl-substituted isocyanatessuch as MONDUR O octadecyl isocyanate.

Preferably, the reaction product is prepared from 1-decene, maleicanhydride, monoethanol amine and octadecyl isocyanate, has an acid valueranging from about 8 to about 15 and a number average molecular weightranging from about 2,000 to about 2,500.

Generally, the powder basecoating composition comprises from about 50 toabout 85 percent by weight of film-forming material and from about 70 toabout 80 percent by weight of the reaction product. Preferably, thereaction product will be included in the powder basecoating compositionfrom about 0.1 to about 5 percent by weight, more preferably, from about0.5 to about 3 percent by weight on the basis of the total weight offilm-forming material and reaction product.

The powder basecoating composition comprises at least one flow controlagent. Suitable as flow control agents are acrylic polymers (preferred),such as polylauryl acrylate, polybutyl acrylate, poly(2-ethylhexyl)acrylate, poly(ethyl-2-ethylhexyl) acrylate, polylauryl methacrylate,polyisodecyl methacrylate and the like, and fluorinated polymers such asesters of polyethylene glycol or polypropylene glycol with fluorinatedfatty acids, e.g., an ester of polyethylene glycol having a molecularweight over about 2,500 and perfluorooctanoic acid. Polymeric siloxaneswith molecular weights over 1,000 may also be used as a flow controlagent, for example, polydimethylsiloxane or poly(methylphenyl)siloxane.The flow control agents can aid in reduction of surface tension duringheating of the powder and in eliminating crater formation. Preferably,the flow control agent is an acrylic copolymer prepared from2-ethylhexyl acrylate and butyl acrylate, such as RESIFLOW PL200available from Estron Chemical of Calvert City, Ky. Generally, the flowcontrol agent is present in amounts from about 0.05 to about 5 percentby weight based on the total weight of the powder coating composition.

The powder base coating composition further comprises at least onevisual effect additive, such, as flake or plate pigments, or metallizedpolymeric particles. Examples of flake pigments include aluminum flakepigments such as Silberline TF4700/LE10521 aluminum flake. Other metalflake compositions may be used such as bronze flake, stainless steelflake, nickel flake, tin flake, silver flake, copper flake and the like.Preferred flake pigments range from 1.0 to 50.0 micron in size. Inaddition to the flake pigments described, other metallized polymericparticles, such as aluminized Mylar and aluminized polyester fibers, maybe used. Other suitable pigments include micas, coated micas, ironoxides, lead oxides, carbon black, titanium dioxide and colored organicpigments such as phthalocyanines. Suitable metal oxides used as coatingson mica particles can comprise aluminum oxides or other metal oxidessuch as titanium dioxide, ferric oxide, chromium hydroxide, and the likeand combinations thereof. Other useful pigments include HELICONE HCsilicone liquid crystal platelets.

The specific pigment to binder ratio can vary widely so long as itprovides the requisite hiding at the desired film thickness andapplication solids. The pigment is incorporated into the powder coatingat a level of 0.1% to 20.0% based on the total weight of the powdercoating. Preferably, the amount of flake pigment is between 1.0% and10.0% based on total weight of the coating composition.

In order for the attractive visual effects caused by the orientation ofthe flake pigment in the resultant coating to be realized, the flakepigment particles are incorporated into the powder coating by dryblending rather than extrusion. The dry blending operation can beconducted with cooling or with heating. Dry blending with heat isreferred to as “bonding”. The bonding method is believed to attach theflake pigment to the binder particles, but not to actually disperse theflake pigment in the binder powder particles. The “bonding” method ofdispersion is particularly useful in the dispersion of metal flakeparticles since it eliminates the undesirable electrostatic effects thatoccur in the electrostatic spraying of metallic particles.

In addition to the colored flake pigments, one or more additionalnon-flake pigments can be included in the coating composition typicallyin amounts from about 1 to about 50 percent by weight, based on thetotal weight of the powder coating composition. Pigments which aresuitable for powder coating compositions may be organic or inorganic andinclude basic lead silica chromate, titanium dioxide, ultramarine blue,phthalocyanine blue, phthalocyanine green, carbon black, black ironoxide, chromium green oxide, ferrite yellow and quinto red.

Anti-popping agents can be added to the compositions to allow anyvolatile material present to escape from the film during baking. Benzoinand/or zinc oxide are preferred degassing agents and when used ispresent amounts ranging from about 0.5 to about 3 percent by weightbased on total weight of the powder basecoating composition. The powdercoating compositions may also preferably contain UV absorbing agents,such as TINUVIN, which when used are typically present in thecompositions in amounts of about 0.5 to about 6 percent by weight basedon the total weight of the powder basecoating composition.

In addition, the powder basecoating composition may contain fumed silicaor the like as a powder flow additive to reduce caking of the powderduring storage. An example of fumed silica is sold by Cabot Corporationunder the trademark CAB-O-SIL®. The powder flow additive, when used, isgenerally present in amounts ranging from about 0.1 to about 0.5 percentby weight based on the total weight of the powder basecoatingcomposition. The powder flow additive is generally added to theparticulate powder basecoating composition after preparation of theparticulate mixture.

The powder coatings compositions are typically prepared by blending thepolymers containing the functional groups, crosslinking agents (forthermosetting compositions) and optional ingredients for 15 minutes in aHenschel blade blender. The powder is then usually extruded such asthrough a Baker-Perkins twin-screw extruder. The extrudate isparticulized typically by first chipping into flake and then milling ina hammer mill. The finished powder can be then classified to a particlesize of usually between 20 and 30 micrometers in a cyclonegrinder/sifter.

An example of a suitable powder basecoat is ENVIROCRON PZB53100 powderbase coat available from PPG Industries, Inc.

The colored powder coating can be applied by electrostatic spraying orby the use of a fluidized bed. Electrostatic spraying using a gun orbell at 55 to 80 kV, 80 to 120 grams or more per minute is preferred.The powder basecoating composition can be applied in one pass or inseveral passes to provide a film thickness after cure of about 12.7 toabout 102 micrometers (0.5 to about 4 mils). Preferred coating thicknessis such that good chip resistance, U.V. opacity, and visual hiding arerealized. Preferred film thickness is 51 to 102 micrometers (2 to 4mils). The substrate to be coated can optionally be preheated prior toapplication of the powder to promote a more uniform powder deposition.

After application of the color powder basecoating to the substrate, thesubstrate is heated to a temperature sufficient to melt and coalesce thecoating. This is an important step in the present invention because whendone correctly the flake pigment migrates to the air interface andaligns itself in a substantially parallel direction to the substrate,resulting in a distinctive, visually pleasing appearance. The heatingstep should be conducted such that the color powder coating coalesces toa substantially continuous fluid layer, but not so high as to causeviscosity increase and crosslinking of the coating before the flakepigment rises to the coating-air interface and aligns with the coatingsurface. The layer is maintained in the fluid state for a period of timesufficient for the flake pigment to rise to the coating-air interfaceand to align so that the two largest dimensions of the pigment flake arealmost parallel with the coating surface. After the pigment has aligneditself with the coating surface, the coating may continue to be heateduntil, in the case of thermoset powder basecoats, partial or completecure is accomplished. Alternatively, the coating may be cooled prior tocure. Typically, the color coat is heated to a temperature between about110° C. and about 190° C. for a period of about 4 to about 40 minutes.When a heat curable thermosetting clear coat is used, the color coatdoes not have to be completely cured and complete cure can occur duringthe cure cycle of the thermosetting clear coat.

A topcoat is deposited over the basecoat and cured to provide thecomposite coated substrate of the present invention. The topcoat can beliquid or powder slurry (powder suspended in a liquid), as desired.Preferably, the topcoating composition is a crosslinkable coatingcomprising one or more thermosettable film-forming materials and one ormore crosslinking materials such as are discussed above. Usefulfilm-forming materials include epoxy-functional film-forming materials,acrylics, polyesters and/or polyurethanes. The topcoating compositioncan include additives such as are discussed above for the basecoat, butpreferably not pigments. If the topcoating is a liquid or powder slurry,volatile material(s) are included. Suitable waterborne topcoats aredisclosed in U.S. Pat. No. 5,098,947 (incorporated by reference herein)and are based on water soluble acrylic resins. Useful solvent bornetopcoats are disclosed in U.S. Pat. Nos. 5,196,485 and 5,814,410(incorporated by reference herein) and include epoxy-functionalmaterials and polyacid curing agents. An example of a useful solventborne topcoats is DIAMOND COAT DCT5555 solvent borne clearcoatingcomposition available from PPG Industries, Inc. Suitable powder slurrytopcoating compositions include those disclosed in InternationalPublications WO 96/32452 and 96/37561, European Patents 652264 and714958, and Canadian Pat. No. 2,163,831, which are incorporated byreference herein.

The amount of the topcoating composition applied to the substrate canvary based upon such factors as the type of substrate and intended useof the substrate, i.e., the environment in which the substrate is to beplaced and the nature of the contacting materials. Generally, thetopcoating composition is applied to provide a film thickness after cureof about 12.7 to about 102 micrometers (0.5 to about 4 mils), preferablyabout 38.1 to about 68.6 micrometers (1.5 to about 2.7 mils). Typically,the topcoat is heated to a temperature between about 110° C. and about190° C. for a period of about 4 to about 40 minutes.

Another aspect of the present invention is a process for coating ametallic or polymeric substrate, comprising the steps of: (a) applyingthe powder basecoating composition discussed above to a surface of ametallic or polymeric substrate, to form a powder basecoat on thesurface of the substrate; (b) at least partially curing the powderbasecoat to form a basecoat; (c) applying a liquid or powder slurrytopcoating composition over at least a portion of the basecoat; and (d)at least substantially curing the topcoating composition and any uncuredbasecoat to provide a composite coating upon the surface of thesubstrate.

As used herein, the term “cure” as used in connection with acomposition, e.g., “composition when cured,” and “thermoset” as used inconnection with a composition, e.g. “thermoset composition” shall meanthat any crosslinkable components of the composition are at leastpartially crosslinked. In certain embodiments of the present invention,the crosslink density of the crosslinkable components, i.e., the degreeof crosslinking, ranges from 5% to 100% of complete crosslinking. Inother embodiments, the crosslink density ranges from 35% to 85% of fullcrosslinking. In other embodiments, the crosslink density ranges from50% to 85% of full crosslinking. One skilled in the art will understandthat the presence and degree of crosslinking, i.e., the crosslinkdensity, can be determined by a variety, of methods, such as dynamicmechanical thermal analysis (DMTA) using a TA Instruments DMA 2980 DMTAanalyzer conducted under nitrogen. This method determines the glasstransition temperature and crosslink density of free films of coatingsor polymers. These physical properties of a cured material are relatedto the structure of the crosslinked network.

The thickness of the sintered and crosslinked composite coating isgenerally about 0.2 to about 5 mils (5 to 125 micrometers), andpreferably about 0.4 to about 4 mils (10 to 100 micrometers). Thecomposite coating is cured such that any crosslinkable components of thecoating are crosslinked to such a degree that the automobile industryaccepts the coating process as sufficiently complete to transport thecoated automobile body without damage to the coating.

Illustrating the invention are the following examples which, however,are not to be considered as limiting the invention to their details.Unless otherwise indicated, all parts and percentages in the followingexamples, as well as throughout the specification, are by weight.

EXAMPLES

The following examples show the preparation of a coated panel by themethod of the present invention using a cleaned and pretreatedgalvanized substrate (optionally coated with an electrodepositedprimer), powder color coat and liquid clearcoat. For the purpose ofcomparison, a panel was coated by a conventional method using anelectrodeposited primer, a liquid color coat and a liquid clearcoat. Thecoated panels were compared for various properties as shown in theTables that follow.

Preparation of Pretreated Panels

Two-sided hot dipped GALVANEAL panels from USX Corporation, 15.3centimeters (cm) wide and 38.1 centimeters (cm) long, were cleaned in aspray tank with CHEMKLEEN 163 cleaner solution (CHEMKLEEN 163concentrate dissolved in tap water at a concentration of 2% on a volumebasis) for 2 minutes at 60° C. (135-145° F.). The panels were rinsedwith deionized water and dried with a warm air blower. The time durationof the cleaning step was adjusted to cause the rinse water to drain fromthe vertical surface of the metal panel in a sheet with no breaks in thewater, thus indicating an oil-free surface. The cleaned panels were thenpretreated with CHEMPHOS C700/C59 Zinc phosphate composition on bothsides and then rinsed with deionized water and dried with a warm airblower. The dried panels were wrapped in paper and stored under ambientroom conditions.

Preparation of Electrodeposited Coated Panels

ED6100H electrodepositable primer (available from PPG Industries, Inc.)was applied by electrodeposition to selected pretreated panels and thepanels were baked for 20 minutes at 177° C. (350° F.) to provide a filmthickness of 20 to 30 micrometers (0.8 to 1.2 mils).

Example A Preparation of GALVANEAL Powder Base Coat/Liquid Clear CoatExample A1

ENVIROCRON PZB53100 powder base coat containing colored mica pigment(available from PPG Industries, Inc.) was applied to the pretreatedpanels by electrostatic spray and the panels were baked for 30 minutesat 172° C. (340° F.) in an electric box oven and allowed to air cool toprovide a film thickness of 43 to 70 micrometers (1.7 to 2.8 mils).

The ENVIROCRON PZB53100 powder base coat included carboxylic acidfunctional polyester resin, beta hydroxy alkylamide crosslinker,acrylate copolymer, reaction product as described below, degassingagents, antioxidant, UV absorber and pigments.

The reaction product was prepared by the following method. A reactionvessel fitted with a condenser, thermometer, nitrogen sparging inlet andagitator was charged with 61.1 parts by weight (ppw) of 1-decenedissolved in 73.8 ppw of butyl acetate. The 1-decene solution was heatedto a reflux temperature at 145° C. and a mixture of 1.8 ppw oftertiary-amyl peroxyacetate (60% by weight in mineral spirits) availableas LUPERSOL 555-M60 and 62.7 ppw of butyl acetate was added over aperiod of about three hours. A solution of 27.4 ppw of maleic anhydridein 98.8 ppw of butyl acetate was added over a period of about two hours.The reaction mixture was thinned with an additional 85.5 ppw of butylacetate followed by heating at reflux for one hour. Monoethanolamine(16.2 ppw) and 16.2 ppw of butyl acetate were added to the reactionmixture and the reaction mixture heated to reflux and water removed byazeotropic distillation when the water content of the reaction mixturewas reduced to less than 0.2% by weight. The temperature of the reactionmixture was set to 115° C. and 1.6 ppw of octadecyl isocyanate dissolvedin 30.0 ppw of butyl acetate was added to the reaction mixture. Thereaction mixture was maintained at 115° C. until there was no evidenceof NCO by IR analysis. Thereafter, solvent was removed by distillationuntil the reaction mixture reached a solids content of 65% by weight.

After application of the powder basecoat as described above, DIAMONDCOAT DCT5555 solvent borne clear composition (available from PPGIndustries, Inc.) was then applied to the powder base coat by sprayapplication and was baked for 30 minutes at 141° C. (285° F.) to providea film thickness of 38 to 64 micrometers (1.5 to 2.6 mils).

Alternately

Example A2

ENVIROCRON PZB53100 powder base coat containing colored mica pigment wasapplied to the pretreated panels by electrostatic spray and the panelswere baked for 19 minutes at 143° C. (290° F.) in an electric box ovenand allowed to air cool to provide a film thickness of 43 to 70micrometers (1.7 to 2.8 mils).

DIAMOND COAT DCT5555 solvent borne clear composition was then applied tothe powder base coat by spray application and was baked for 30 minutesat 169° C. (335° F.) to give a film thickness of 38 to 64 micrometers(1.5 to 2.6 mils).

Example B Preparation of GALVANEAL/Electrodeposited Primer/Powder BaseCoat/Liquid Clear Coat Example B1

ENVIROCRON PZB53100 powder base coat containing colored mica pigment wasapplied to the electrodeposited primer panels by electrostatic spray andthe panels were baked for 30 minutes at 172° C. (340° F.) in an electricbox oven and allowed to air cool to give a film of 43 to 70 micrometers(1.7 to 2.8 mils).

DIAMOND COAT DCT5555 solvent borne clear composition was then applied tothe powder base coat by spray application and was baked for 30 minutesat 141° C. (285° F.) to give a film thickness of 38 to 64 micrometers(1.5 to 2.6 mils).

Alternately

Example B2

ENVIROCRON PZB53100 powder base coat containing colored mica pigment wasapplied to the electrodeposited primer panels by electrostatic spray andthe panels were baked for 19 minutes at 143° C. (290° F.) in an electricbox oven and allowed to air cool to give a film of 43 to 70 micrometers(1.7 to 2.8 mils).

DIAMOND COAT DCT5555 solvent borne clear composition was then applied tothe powder base coat by spray application and was baked for 30 minutesat 169° C. (335° F.) to give a film thickness of 38 to 64 micrometers(1.5 to 2.6 mils).

Control (Comparative)

Preparation of Control Panels Coated with Conventional Liquid. System

Liquid Waterborne HWB190430 basecoat containing colored mica pigment(available from PPG Industries Inc.) was applied to the electrodepositedprimer panels by spray application and the panels were baked for 10minutes at 121° C. (250° F.) in an electric box oven and allowed to aircool to give a film of 20 to 38 micrometers (0.8 to 1.5 mils).

DIAMOND COAT DCT5555 solvent borne clear composition was then applied tothe powder base coat by spray application and was baked for 30 minutesat 141° C. (285° F.) to give a film thickness of 38 to 64 micrometers(1.5 to 2.6 mils).

Comparison of Panels

The following tables show a direct comparison of panels coated by themethod of the present invention (Examples A and B) and panels coatedwith a commercial paint system (Control). The panels prepared by theprocess of the present invention are generally equal to those of thecontrol with respect to the following automotive test properties: 20°gloss (ASTM D523-89), chip resistance (ASTM 3170-03), scratch resistance(Chrysler Test LP-463-PB-54-01 crock-mar test: 20° gloss retention), Drycross-hatch adhesion (ASTM D3359 Method A), humidity resistance (ASTMD1735-02 for 240 hrs at 100° F. and 100% relative humidity), durability(24 months Florida Exposure, SAE J1976) and salt spray corrosionresistance (ASTM B117-95).

TABLE 1 Example A Control Primer Layer None ED6100H Base Coat ENVIROCRONPowder Liquid-Waterborne PZB53100 HWB190430 Clear Coat DIAMOND COATDIAMOND COAT DCT5555 DCT5555 Example A1 Example A2 Control Base CoatBake Full Bake Flash Bake Flash Bake 30′ @ 340° F. 19′ @ 295° F. 10′ @250° F. Clear Coat Bake Normal Bake High Bake Normal Bake 30′ @ 285° F.30′ @ 335° F. 30′ @ 285° F. 20° Gloss 80-95 80-95 80-95 ASTM D523-89Chip Resistance 7-8 7-8 7-8 ASTM 3170-03 (Scale: 1 = poor/10 =excellent) Scratch Resistance 60-70% 65-75% 60-70% Chrysler TestLP-463-PB-54-01 (crock-mar test: 20° gloss retention) Adhesion 100% 100%100% ASTM D3359 Method A Dry crosshatch adhesion Humidity resistance100% 100% 100% Adhesion Adhesion Adhesion ASTM D1735-02 No Blisters NoBlisters No Blisters (240 hrs 100° F. No Blush No Blush No Blush 100%relative No Cracking No Cracking No Cracking humidity) Durability (24months Florida Exposure) SAE J1976 % 20° gloss Retention 80-88 80-8880-88 Blister/Blush None/None None/None None/None Acid Etch Slight- V.Slight- Slight- Moderate Slight Moderate Corrosion Resistance: ASTMB117-95 Salt Spray 500 hrs Salt Spray Scribe Creep (mm) 3-6 mm 3-6 mm2-6 mm Blister Size/Density Very Small/ Very Small/ Very Small/ Very FewVery Few Very Few

TABLE 1 Example B Control Base Coat ENVIROCRON Powder Liquid-WaterbornePZB53100 HWB190430 Clear Coat DIAMOND COAT DIAMOND COAT DCT5555 DCT5555Example B1 Example B2 Control Base Coat Bake Full Bake Flash Bake FlashBake 30′ @ 340° F. 19′ @ 295° F. 10′ @ 250° F. Clear Coat Bake NormalBake High Bake Normal Bake 30′ @ 285° F. 30′ @ 335° F. 30′ @ 285° F. 20°Gloss 80-95 80-95 80-95 ASTM D523-89 Chip Resistance 7-8 7-8 7-8 ASTM3170-03 (Scale: 1 = poor/10 = excellent) Scratch Resistance 60-70%65-75% 60-70% Chrysler Test LP-463-PB-54-01 (crock-mar test: 20° glossretention) Adhesion 100% 100% 100% ASTM D3359 Method A Dry crosshatchadhesion Humidity resistance 100% 100% 100% Adhesion Adhesion AdhesionASTM D1735-02 No Blisters No Blisters No Blisters (240 hrs 100° F. NoBlush No Blush No Blush 100% relative No Cracking No Cracking NoCracking humidity) Durability (24 months Florida Exposure) SAE J1976 %20° gloss Retention 80-88 80-88 80-88 Blister/Blush None/None None/NoneNone/None Acid Etch Slight- V. Slight- Slight- Moderate Slight ModerateCorrosion Resistance: ASTM B117-95 Salt Spray 500 hrs Salt Spray ScribeCreep (mm) 2-6 mm 2-6 mm 2-6 mm Blister Size/Density Very Small/ VerySmall/ Very Small/ Very Few Very Few Very Few

The above comparative examples show that the coating system of Example Bof the present invention compares very favorably with the conventionalcoating system in the physical property tests set forth above. Thecoating system of the present invention can be used with or withoutelectrodeposited primer, which provides greater flexibility than theconventional coating process, particularly with regards to capability,efficiency and cost.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications that are within the spirit and scopeof the invention, as defined by the appended claims.

1. A composite coated substrate comprising: (a) a substrate selectedfrom the group consisting of metallic substrates, polymeric substratesand combinations thereof, wherein a surface of the substrate isessentially free of a primer coating; (b) a basecoat deposited upon thesurface of the substrate, the basecoat being formed from a powderbasecoating composition comprising: (i) at least one film-formingmaterial comprising a thermosettable polyester and a curing agent; (ii)at least one reaction product of at least one cyclic carboxylic acidanhydride, at least one alkene and at least one reactant selected fromthe group consisting of primary amines, aliphatic polyamines, primaryamino alcohols, alcohols, isocyanates and mixtures thereof, thecopolymer having a number average molecular weight ranging from about1,000 to about 20,000; and (iii) at least one flow control agent; and(c) a topcoat deposited from a liquid or powder slurry topcoatingcomposition applied over the basecoat to provide a composite coatedsubstrate.
 2. The composite coated substrate according to claim 1,wherein the primer coating is a weldable primer coating.
 3. Thecomposite coated substrate according to claim 1, wherein the primercoating is an electrodeposited primer coating.
 4. The composite coatedsubstrate according to claim 1, wherein the surface of the metallicsubstrate is bare metal.
 5. The composite coated substrate according toclaim 4, wherein the bare metal is cold-rolled steel.
 6. The compositecoated substrate according to claim 4, wherein the bare metal isgalvanized steel.
 7. The composite coated substrate according to claim1, wherein the surface of the metallic substrate is pretreated with apretreatment composition prior to application of the composite coating.8. The composite coated substrate according to claim 7, wherein thepretreatment coating comprises zinc phosphate or iron phosphate.
 9. Thecomposite coated substrate according to claim 1, wherein thethermosettable polyester has reactive functional groups selected fromthe group consisting of hydroxyl, carboxylic acid, epoxy, carbamate,amide, carboxylate and combinations thereof.
 10. The composite coatedsubstrate according to claim 1, wherein the curing agent is selectedfrom the group consisting of aminoplasts, blocked polyisocyanates,polyacids, polyepoxides, polyols, polyanhydrides, hydroxyalkylamides,and mixtures thereof.
 11. The composite coated substrate according toclaim 1, wherein the cyclic carboxylic acid anhydride is selected fromthe group consisting of maleic anhydride, chloromaleic anhydride,dichloromaleic anhydride, bromomaleic anhydride, citraconic anhydride,dimethylmaleic anhydride, ethylmaleic anhydride, itaconic anhydride,vinylsuccinic anhydride and vinyl trimellitate anhydride.
 12. Thecomposite coated substrate according to claim 1, wherein the alkene isselected from the group consisting of cycloalkenes, alpha olefins, vinylmonomers, esters of acrylic acid or methacrylic acid, and mixturesthereof.
 13. The composite coated substrate according to claim 1,wherein the reactant is a primary amino alcohol selected from the groupconsisting of ethanolamine and propanolamine.
 14. The composite coatedsubstrate according to claim 1, wherein the flow control agent is anacrylic polymer.
 15. The composite coated substrate according to claim1, wherein the powder basecoating composition further comprises at leastone visual effect additive selected from the group consisting of flakeor plate pigments and metallized polymeric particles.
 16. The compositecoated substrate according to claim 1, wherein the flake pigment isaluminum coated mica or metal oxide-coated mica.
 17. A composite coatedsubstrate comprising: (a) a substrate selected from the group consistingof metallic substrates, polymeric substrates and combinations thereof,wherein a surface of the substrate is free of a primer coating; (b) abasecoat deposited upon the surface of the substrate, the basecoat beingformed from a powder basecoating composition comprising: (i) at leastone film-forming material comprising a thermosettable polyester and acuring agent; (ii) at least one reaction product of at least one cycliccarboxylic acid anhydride, at least one alkene and at least one reactantselected from the group consisting of primary amines, aliphaticpolyamines, primary amino alcohols, alcohols, isocyanates and mixturesthereof, the copolymer having a number average molecular weight rangingfrom about 1,000 to about 20,000; and (iii) at least one flow controlagent; and (c) a topcoat deposited from a liquid or powder slurrytopcoating composition applied over the basecoat to provide a compositecoated substrate.
 18. A process for coating a metallic or polymericsubstrate, comprising the steps of: (a) applying a powder basecoatingcomposition to a surface of a metallic or polymeric substrate, whereinthe surface is essentially free of a primer coating, the first powderbasecoating composition comprising: (i) at least one film-formingmaterial comprising a thermosettable polyester and a curing agent; (ii)at least one reaction product of at least one cyclic carboxylic acidanhydride, at least one alkene and at least one reactant selected fromthe group consisting of primary amines, aliphatic polyamines, primaryamino alcohols, alcohols, isocyanates and mixtures thereof, thecopolymer having a number average molecular weight ranging from about1,000 to about 20,000; and (iii) at least one polymer flow controlagent, to form a powder basecoat on the surface of the substrate; (b) atleast partially curing the powder basecoat to form a basecoat; (c)applying a liquid or powder slurry topcoating composition over at leasta portion of the basecoat; and (d) at least substantially curing thetopcoating composition and any uncured basecoat to provide a compositecoating upon the surface of the substrate.
 19. A process for coating ametallic or polymeric substrate, comprising the steps of: (a) applying apowder basecoating composition to a surface of a metallic or polymericsubstrate, wherein the surface is free of a primer coating, the firstpowder basecoating composition comprising: (i) at least one film-formingmaterial comprising a thermosettable polyester and a curing agent; (ii)at least one reaction product of at least one cyclic carboxylic acidanhydride, at least one alkene and at least one reactant selected fromthe group consisting of primary amines, aliphatic polyamines, primaryamino alcohols, alcohols, isocyanates and mixtures thereof, thecopolymer having a number average molecular weight ranging from about1,000 to about 20,000; and (iii) at least one polymer flow controlagent, to form a powder basecoat on the surface of the substrate; (b) atleast partially curing the powder basecoat to form a basecoat; (c)applying a liquid or powder slurry topcoating composition over at leasta portion of the basecoat; and (d) at least substantially curing thetopcoating composition and any uncured basecoat to provide a compositecoating upon the surface of the substrate.